NEFL and autoimmune polyendocrinopathy: Furthermore, due to different blood levels in various neurodegenerative parkinsonian syndromes, NfL might serve as biomarker to distinguish between atypical parkinsonian syndromes (APS) and PD, even in early stages of APS, when clinical symptoms are yet inconclusive (Hansson et al. 2017; Marques et al. 2019).